Valve Adjust

Just re-shimmed my valves. They were all at the outer limits of spec. Seems like they are all well within limits now but I am afraid of firing her up. Done valves before and know how to read the feeler guages. What are the consequences of too tight or too loose?

Any One?

If you are too loose then the buckets can bounce underneath the cam and damage the lobes, plus the bike will be very hard to start. If it is too tight then the cam lobes can actually wear and further round out the lobes and it may also be hard to start, do to the valve being pushed slightly open. When I adjust my valves I try to make them a little bit on the loose side, but still in spec. Better a little loose then a little tight.

I checked my valves recently for the first time in one year. Yes, I know that was very bad. The valves are within parameters but on the tightest side, both intake and exhaust. Since they are still within parameters, I closed the motor up and left them alone. This is the first time that I did any valve clearance check.

What generally makes valves go too tight or too loose?

This is what me and my dad came up with. Your valves get pushed up into the head to make them tighter. The valve spring constantly pushes onto the valve which sucks it up into the head little by little. They get looser because that shim bounces underneath the bucket so slightly that it wears it out a little bit. Im fairly sure thats the reason they get tighter and looser. Anyone wanna confirm this? Plus I usually only check my valves if I can hear them or if it doesnt start easily enough or if it runs funny.

Some possibilities for tight valves; valve seat wear (head & valve), valve head tulips, valve stem stretches.

For loose valves: cam lobe wear....

...What generally makes valves go too tight or too loose?

Loose is caused by excess or abnormal wear. Too tight is the way its supposed to end up with normal wear. Its usually caused by the valves wearing into the seats, either one or both sides wear. On a new bike, the angles are at 1' difference for better sealing and will settle in as it wears in, raising the stem height. This is why they like a vavle adjustment at the 500 mile mark on new bikes. Also valve stem stretch can also create tight clearances. If you run at high rpm's all the time, ie aggressive racing etc, you may want to have a valve change interval in your schedule. They only stretch so far, then the stem tip comes apart, this releases the valve into the cylinder and it gets real ugly from there.

You can also help yourself out by using high quality oil and changing it on a regular basis(hours of operation--not time of year method) Dirty oil will accelerate all kinds of engine wear, but especially valve train wear. WR Dave.

caused by the valves wearing into the seats

What he said.

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